To a certain extent, the present invention was inspired by attempting to solve the problem of drilling multiple holes in printed circuit boards which, even in small sizes, frequently have a very substantial number of holes of varying diameters drilled in precise patterns therein for purposes of receiving connecting pins, contacts or wires on various electrical components which are integrally fixed to the printed circuit on the board by soldering. Drilling such a multiplicity of holes has heretofore been a very time-consuming operation, the crudest methods comprising individually drilling said holes by a single drill mounted either in a drill press or in a numerically controlled drilling machine having a limited number of variably movable drill heads. The close relationship of said holes in such circuit boards renders the drilling thereof by automatic means very difficult in view of the need to simultaneously operate a plurality of drills in a precise pattern without conflict between the various drills which must be powered, and also sometimes requiring the changing of drill bits to form a plurality of diameters occasionally required.
It has been the practice in certain manufacturing operations to operate a multiplicity of drills by various power means where the close proximity of the holes drilled thereby is not as acute as found in the drilling of holes in printed circuit boards. For example, in drilling spaced holes in ladder rails for receiving the ends of the rungs of the ladder by means of a gang of drills is well-known and providing power means to operate such drills simultaneously is readily solved by gear trains, chains, or otherwise. Further, gang drilling machines which have adjustable mounts for the drills to accommodate the same to different patterns also are known, and examples of these are included among the following patents, which are typical of mechanically-operated drilling machines in which the drills are operated by gears or otherwise, as referred to above:
U.S. Pat. No. 2,215,273 Paradis: Sept 17, 1940 PA0 U.S. Pat. No. 3,635,570 DeGelleke et al: Jan 18, 1972 PA0 U.S. Pat. No. 3,765,787 Hart et al: Oct. 16, 1973 PA0 U.S. Pat. No. 3,822,958 Lewis: July 9, 1974 PA0 U.S. Pat. No. 4,090,803 Haley: May 23, 1978 PA0 U.S. Pat. No. 3,025,728 Cross et al: Mar. 20, 1962 PA0 U.S. Pat. No. 3,310,796 Sanders: Mar. 21, 1967 PA0 U.S. Pat. No. 3,381,550 Smith: May 7, 1968 PA0 U.S. Pat. No. 3,627,437 Smith: Dec. 14, 1941 PA0 U.S. Pat. No. 3,669,557 Mitchell: June 13, 1972 PA0 U.S. Pat. No. 3,747,085 Bala et al: July 17, 1973
Another problem existing in the operation of gang drills comprises detecting either malfunctioning individual drills or broken drill bits, especially when mass production is involved, and efforts have been made heretofore to provide various types of detecting means for such broken bits or malfunctioning power means, and typical examples of such devices are illustrated in the following patents:
Forming a support means for a multiplicity of drills also has been a problem requiring attention heretofore but especially where the proximity of the holes to be drilled is not acute, compared to drilling of holes in printed circuit boards, it has not been particularly difficult to devise supports and mounting means for a plurality of drill shanks or chucks, but especially where drill holes are in very close proximity, as in printed circuit boards, some means for forming a support for a plurality of preferably small size power heads has given rise to the investigation of employing suitable means and methods for forming such support means of rigid sheet-like type and investigations of suitable solutions for providing such support means comprises the subject matter of the present invention. In this, as described in greater detail hereinafter, the basic support plate is formed by drilling in a set of similar sizes and shapes of rigid sheet material, such as metal or plastic, partial patterns of holes comprising parts of a complete pattern of holes to provide support for powered drill heads positioned on said plates in a manner not to conflict with each other and operable successively upon product sheet material to form a desired complete pattern of holes therein.